This invention relates to an apparatus for melting frozen water off of a roof, and specifically to a system which will prevent or melt an ice dam formed on a roof valley, commonly found on commercial and residential roofs. Although the invention is described and illustrated herein in use on a roof valley, it is suitable for melting or preventing ice in a variety of other applications.
It is typical in many parts of the world that two to three feet of snow may build up on a roof surface and in the valleys. Roof valley ice formation occurs generally as result of melting snow that has accumulated on the surface of the roof. Water from the melting snow may freeze when the ambient temperature drops below freezing or when the water contacts a colder region of the roof valley. Under some circumstances, this freezing water may create ice dams which can be both dangerous and destructive.
One way in which ice dams form is on a roof which has inadequate insulation and is of what is referred to herein as single roof construction. Built-up snow is a good insulator and any heat loss from inside the building that reaches the exterior single roof surface melts a very thin layer of snow, forming a snow-water interface between the roof valley surface, which is often made of metal, and the lower surface of the snow. If the ambient temperature falls below freezing, the water will freeze and begin the formation of an ice dam. These ice dams may contain water and can cause interior leakage as the water finds its way underneath various types of exterior roofing material. Additionally, because the water and snow are retained on the roof, the weight build up can result in structural failure.
Such roof valley ice dams are, however, not limited to roofs which are not adequately insulated. A double roof, referred to as a cold roof, is built with a vented air space between the primary roof and an exterior roof. This is supposed to prevent any building heat loss from reaching the exterior surface of the roof and generally is effective in preventing melting at the bottom of the snow layer as the result of escaping heat. However, as the ambient temperature rises to near freezing (32.degree. F.) the snow begins to melt along the roof peak, the water from the melting snow flows down the valleys and underneath the snow blanket, and ice formation occurs. Additionally, double or cold roofs are always vented at the roof peak to allow the warm air to escape from the air space between the two roof surfaces. This warm air aids in melting the snow at the peak and contributes to ice dam formation. Furthermore, snow accumulated on roof peaks is typically exposed to solar energy for longer periods than snow accumulated in roof valleys. Thus, snow on a roof peak is more likely to melt when the ambient temperature is near freezing than is snow in a valley below the peak.
Regardless of how valley ice formations occur, their presence can be extremely dangerous to passersby as they may be struck by falling ice and snow and seriously injured. Additionally, ice formation can result in serious damage to a building.
Most prior solutions to the problem of snow and ice accumulation on roofs have focused exclusively on roof eaves. Such a system is described in U.S. Pat. No. 5,391,858 entitled ICE DAM MELTING SYSTEM, the disclosure of which is incorporated herein by reference. Other solutions, while addressing the problem of roof valleys as well as roof eaves, are complex and difficult to assemble. For example, see U.S. Pat. No. 3,691,343 entitled MODULAR SYSTEM OF ROOF HEATER SHINGLES.